Formerly captive ferrets are thriving at Rocky Mountain Arsenal, and their wild babies are fierce

Dozens of slinky, ferocious and rare ferrets are settling in and making babies at their new home in Colorado, one year after they were released at a wildlife refuge outside Denver.

Black-footed ferrets are making wild babies at Rocky Mountain Arsenal National Wildlife Refuge. (Ryan Hagerty, U.S. Fish and Wildlife Service via Flickr)

The U.S. Fish and Wildlife Service counted 47 endangered black-footed ferrets last month at the Rocky Mountain Arsenal National Wildlife Refuge. That includes 20 out of the original 28 captive-born ferrets that were released there in 2015, a survival rate of 71 percent.

“Seventy-one percent is phenomenal for survival,” said Kimberly Fraser, an outreach specialist for the federal ferret program.

Searchers also found nearly two dozen ferrets that were born at the refuge — a promising sign for the campaign to bring the animals back from the brink of extinction.

“Just seeing the first one is an amazing thing,” said David Lucas, the refuge manager. “And to see another, and another, and another…. It was higher than we expected.”

Here’s a look at black-footed ferrets and an update on the program to save them:

About black-footed ferrets

They are furry, weasel-like critters that grow up to 2 feet long and 2½ pounds. They mainly eat prairie dogs.

They’re native to the West, from Canada to Mexico, but their numbers plummeted as prairie dogs were exterminated or died from plague, and ferret habitat was reduced by development.

Black-footed ferrets were once thought to be extinct, but a small colony was discovered in Wyoming in 1981. Researchers have been trying to restore the population since then. They’re protected under the Endangered Species Act.

How many are left?

About 300 live in the wild at 28 reintroduction sites in Arizona, Colorado, Kansas, Montana, New Mexico, South Dakota, Utah and Wyoming, and in the Canadian province of Saskatchewan and the Mexican state of Chihuahua. Nine were released last week at Wind Cave National Park, South Dakota.

Another 300 captive-born ferrets are being prepared for release at six breeding centers.

Black-footed ferrets have been released twice at Rocky Mountain Arsenal Wildlife Refuge, in October 2015 and September of this year. While the 2015 ferrets are doing well, teams found only five of 15 released this year.

Researchers say they’re not worried. The 2016 ferrets were released into the same prairie dog colony as the 2015 group because researchers didn’t realize how many survivors were still there. Some newcomers might have moved to less crowded territory and eluded the counters last month, Lucas said.

How do you count ferrets?

Teams searched for 10 nights at the Colorado refuge last month, using lights to spot the telltale emerald reflection from the ferrets’ night-vision eyes.

Once they located ferrets, searchers placed elongated, burlap-covered traps over their burrows. Because the traps resembled part of the burrow, the naturally curious ferrets climbed in.

Searchers could distinguish captive-born ferrets from those born at the refuge because ID chips were implanted in captive-born animals before their release.

The wild-born ferrets were vaccinated for plague, canine distemper and rabies, implanted with a chip and turned loose again. Captive-born ferrets had been vaccinated before they were originally released at the refuge.

How many is enough?

The Fish and Wildlife Service has a goal of 3,000 breeding adult ferrets in at least 30 populations in at least nine states. At the Rocky Mountain Arsenal refuge, the goal is about 77 to 120 ferrets, said Nick Kaczor, assistant manager of the refuge.

What’s next?

The Fish and Wildlife Service plans to release about 20 more ferrets at the Rocky Mountain Arsenal refuge, but no date has been set, Lucas said. The next release will be in a different part of the refuge.

If the refuge colony thrives, some ferrets born there could be moved to bolster populations in other states because they’ve shown they can survive in the wild.

“Those wild-born ones, man, they were feisty, they were aggressive,” Kaczor said. “You can tell they have that fighting instinct.”

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